Office of Compensation Analysis and Support 

Program Evaluation Report

Document Number: 

OCAS-PER-008 

Effective Date: 04/12/07 

Revision No. 0

Modification of NIOSH-IREP lung cancer risk model: effect of 

“combined” lung model on non-compensable lung cancer claims Page 1 of 4 

Author: Signature on file Date: 04/12/2007 Russell W. Henshaw, Epidemiologist 

Approval: Signature on file Date: 04/12/2007 J.W. Neton, Associate Director for Science 

Supersedes: None 

ISSUE 

AUTHORIZATION 

DATE 

EFFECTIVE 

DATE 

REV. 

NO. DESCRIPTION 

04/12/07 04/12/07 0 

New document to report the impact of the 

NIOSH-IREP lung cancer model on noncompensable cases completed before 2/28/06 

1.0 Description

The “combined” lung cancer risk model was introduced on 02/28/06 via the release of NIOSHIREP Version 5.5, followed by v5.5.1 on 05/16/06. The combined lung model is programmed 

with two different lung cancer risk models: the NIOSH-IREP model, plus an alternative risk 

model created by the National Cancer Institute for use in NIH-IREP, another version of IREP 

(referred to hereafter as the “NIH” model). For each cancer of the lung, trachea, or bronchus, 

NIOSH-IREP now calculates separately the probability of causation (PC) produced by each of 

the two risk models and reports the higher PC at the upper 99th percentile credibility limit as the 

PC value of record for the claim. NIOSH-IREP v5.5 and v5.5.1 also incorporate a bias 

correction factor for random errors in dosimetry for “never smokers” exposed to radon. Due to a 

programming oversight, this correction had been omitted for “never smokers” and was applied 

only to smokers in earlier versions of NIOSH-IREP. NIOSH-IREP v5.5 corrected this error. 

This “combined” lung cancer risk model was endorsed by the Advisory Board on Radiation and 

Worker Health, and can result in no lower PC value for the same set of claim inputs than had 

been calculated under previous versions of NIOSH-IREP (versions 5.4 and earlier). 

For a more detailed description of the new combined model, including the background of and 

rationale for the modification, please refer to OCAS-PEP-008, dated 12/07/06. 
Effective Date: 04/12/07 Revision No. 0 Document No. 

OCAS-PER-008 

Page 2 of 4 

 

2.0 Evaluation

A database search identified 920 non-compensable (PC<50% at the upper 99th percentile 

credibility limit) lung cancer claims that had been processed prior to the adoption of the 

combined lung model. A preliminary evaluation was conducted and the results were reported in 

OCAS-PEP-008. The preliminary evaluation consisted of running each of the 920 claims (729 

[79%] single cancer claims, 191 [21%] multiple cancer claims) in NIOSH-IREP v5.5.1 (single 

IREP run at 2000 iterations) to determine the initial effect of the “combined lung model” on PC. 

The preliminary results reported in the program evaluation plan (OCAS-PEP-008) indicated that 

the PC increased in 73 of the 729 single cancer claims (95 total claims with an increased PC, 

including 22 increases in the multiple cancer claims), and that 11 of the 95 claims had a new PC 

value of 45% or higher and would require further evaluation. However, a subsequent review 

conducted for this PER revealed that a mistake had been made in the PEP. Actually, the PC 

increased in 77 of the single cancer claims (99 increases in total, including the multiple cancer 

claims). However, the PC remained below 45% in all 4 of the additional claims, so no further 

evaluation of those claims was required. The 4 increases were all due to the NIH lung model 

rather than to the radon bias correction factor. 

As expected, the alternative NIH lung cancer risk model produced the higher PC value for the 

vast majority (95, or 96%) of the 99 affected claims. Of these 95 claims, 74 (78%) were single 

cancer claims and 21 (22%) were multiple cancer claims. However, the 21 multiple cancer 

claims included 28 separate lung cancers. Thus, the total number of lung cancers among all 

claims for which the NIH lung model produced a higher PC (versus the NIOSH lung model) was 

102. The mean and median increase in PC produced by the NIH lung model versus the NIOSH 

model for the 102 lung cancers was 1.90 and 1.30 percentage points, respectively (range = 0.01 

to12.58 percentage points). The NIH lung model produced a lower PC value at the upper 99th

percentile credibility limit than the NIOSH lung model for 825 (90%) of the 920 previously noncompensable claims. Corrected results of the preliminary evaluation are displayed in Table 1. 

Of the 99 claims with increased PC values, there were only 4 claims in which the NIOSH v5.5.1 

lung model produced a higher PC than the NIOSH lung model used in earlier versions of 

NIOSH-IREP (v5.4 and earlier). The PC increases for these 4 claims were due to the radon bias 

correction factor (see OCAS-PEP-008, Section 1.0). The PC increases due to the bias correction 

factor were 1.01, 5.23, 5.29, and 6.47 percentage points, respectively (mean increase = 4.50; 

median = 5.26). 
Effective Date: 04/12/07 Revision No. 0 Document No. 

OCAS-PER-008 

Page 3 of 4 

 

Table 1: Preliminary evaluation of non-compensable lung cancer claims processed before 

2/28/06: initial effect of NIOSH-IREP “combined” lung cancer risk model on probability of 

causation (PC) based on single IREP run at 2000 iterations 

Type of 

Claim 

Number 

of 

Claims 

No PC 

Increase 

PC 

Increase 

Increase 

Due to 

NIH 

Model 

Increase 

Due to Bias 

Correction 

Factor 

New 

PC 

<45% 

New PC

= 45 - 

49.99% 

New 

PC 

≥

50%

1 cancer 729 652 77 74 3 70 3 4

>1 cancer 191 169 22 21 1 18 4 0

Totals 920 821 99 95 4 88 7 4

As described above, the PC increased initially (single IREP run at 2000 iterations) in 99 of the 

920 lung claims. The new PC values for 88 (89%) of the 99 claims remained below 45% and 

required no further review. However, 11 (11%) of the 99 claims had a new PC value of 45% or 

higher and merited further evaluation. Each of the 11 claims with a new PC ≥45% required 30 

IREP runs at 10,000 iterations to establish the average (arithmetic mean) PC value and/or a 

rework of the dose reconstruction, depending in part upon the original dose reconstruction 

approach used for the claim. Since 4 of these 11 claims had more than one cancer, 30 IREP runs 

were required for each cancer (i.e., including cancers other than lung) for each of the 4 claims. 

The final outcome for each of the 11 claims is reported in Table 2. 

Table 2: Final evaluation of 11 claims in which the PC value had increased to ≥45% after 

single IREP run at 2000 iterations using NIOSH-IREP v5.5.1 “combined” lung model 

Claim 

No. 

Original 

DR 

Approach 

Original 

Claim PC 

(1 IREP 

Run) 

Interim 

Claim PC

(1 IREP 

Run) 

Interim 

Claim PC

(30 IREP 

Runs) 

Final Claim Outcome 

1 Overestimate 45.91% 46.05% 45.26% PC remained below 50% 

2 Overestimate 45.50% 45.79% 44.94% PC remained below 50% 

3 Best Estimate 46.14% 50.94% 50.05% PC exceeded 50% 

4 Overestimate 38.28% 48.08% 43.33% PC remained below 50% 

5 Overestimate 46.56% 53.03% 49.15% PC fell below 50% after rework 

6 Overestimate 43.81% 49.04% 48.93% PC remained below 50% 

7 Overestimate 44.38% 56.15% N/A Reworked for reasons unrelated to 

lung model; PC decreased to 23.29% 

8 Overestimate 34.35% 46.93% 47.44% PC remained below 50% 

9 Overestimate 44.60% 47.56% 52.17% After “best estimate” rework, 

PC=52.08% (single IREP run) 

10 Overestimate 41.16% 45.08% 45.87% PC remained below 50% 

11 Overestimate 42.72% 53.22% N/A PC decreased to 42.82% after rework 
Effective Date: 04/12/07 Revision No. 0 Document No. 

OCAS-PER-008 

Page 4 of 4 

 

3.0 Resolution/Corrective Action

Of the 920 evaluated lung cancer claims, the “combined” lung cancer risk model produced no PC 

increase in 821 claims. Of the 99 claims with an increased PC value at the upper 99th percentile 

credibility limit, the new PC for 88 of the 99 claims remained below 45% and required no further 

evaluation. Of the 11 claims that merited further evaluation (i.e., PC≥45% after a single IREP 

run at 2000 iterations), the final PC value for 9 of the claims remained below 50% (Table 2) after 

being reworked and/or subjected to 30 IREP runs. 

The final PC increased to ≥50% for only 2 of the claims (Claim #3 and Claim #9, Table 2). 

Since the dose reconstruction for Claim #3 was originally performed as a “best estimate,” no 

further review was necessary and the new PC of 50.05% (average value of 30 IREP runs) was 

considered the final PC result. Claim #9, originally an “overestimate” dose reconstruction, was 

reworked as a “best estimate.” After the rework, a new PC of 52.08% was calculated using the 

default simulation sample size of 2000 and a single IREP run. Since this new PC value exceeded 

52% and was based on a best estimate dose reconstruction, the claim no longer met the criteria 

for conducting 30 IREP runs and the PC value of 52.08% was considered the final PC result. 

Thus, of the 920 non-compensable lung cancer claims completed prior to the 2/28/06 

implementation of the “combined” lung cancer risk model, the final PC after reevaluation 

crossed the 50% compensation threshold in only 2 (0.2%) of the 920 claims. An itemized list 

has been provided to DOL containing the final evaluation result for each of the 920 claims. 

4.0 Reference

1) National Institute for Occupational Safety and Health, Office of Compensation Analysis 

and Support: OCAS-PEP-008 (Program Evaluation Plan: Modification of NIOSH-IREP 

lung cancer risk model: impact of “combined” lung model on non-compensable lung 

cancer claims). December 7, 2006.